Mechanics of Paperboard Packages : Performance at Short Term Static Loading

Abstract: Paper 1Several problems emerge when a paperboard package is modeled by means of the nite element method. One of the issues that one has to deal with is the constitutive model of the paperboard. Paperboard and paper in general areorthotropic materials, which means that constitutive parameters in three orthogonal directions must be determined. Furthermore, the geometry of papersheets makes it dicult to measure the out-of-plane elastic and plastic parameters. In addition, in the case of paperboard, the material parameters ofthe dierent layers must be determined in order to obtain an accurate materialmodel. This report comprises two parts. In the rst part, the implementation ofa constitutive model for paperboard by means of the commercial computationalprograme ABAQUS was discussed. The second part consists of a presentationof some experimental work performed for the validation of the results from thecomputer simulations.Paper 2The aim of this study was to analyse the mechanical behaviour of paperboard packages subjected to static compressive loads. The study was divided into three parts and experiments and nite element analysis conducted for eachpart. First, a panel of paperboard was subjected to edge compressive loadingas a means of checking the material model. Second, the package was cut intosegments and each segment subjected to compression in order to determine thecontribution of the dierent parts to the overall behaviour of the package. Third, a whole package loaded in compression was studied. In the nite element simulations,the paperboard was modeled as an orthotropic, linear, elastic-plasticlaminate. The study utilized a non-linear nite element analysis based on theplasticity of the material and large displacements. The results show that themiddle segment of the package exhibits a higher stiness than that of the upperand lower package segments and that of the whole package, which leads to theconclusion that the low initial stiness of the package is a consequence of thelow stiness of the upper and lower corners, i.e. of the horizontal creases.Paper 3The study of a paperboard package subjected to vertical compression presents several complicated issues. A nite element simulation of such a package has to take into account both the material non-linearity and the geometrical nonlinearity due to large deformations. Previous work concerning the nite element modelling of a whole package has shown that it is dicult to achieve the correct stiness in the nite element model without adopting a more accurate model for the creases in the paperboard package. This paper proposes a new approach in modelling the paperboard creases, using a special nite element for the creases. The element is of a feedback link type, giving stiness as a function of displacement at its nodes. Experiments were conducted in order to determine the behaviour of the creases during compression and the results were used to implemen the special element with the capability of behaving as a crease. The element was tested with good results in the models of a creased panel, a package segment and a whole package. The proposed approach to modelling the creases opens up new possibilities for the design of creases and, consequently, of the whole package.